Prevalence of feline coronavirus types I and II in cats with histopathologically verified feline infectious peritonitis

Abstract

Feline coronaviruses (FCoV) vary widely in virulence causing a spectrum of clinical manifestations reaching from subclinical course to fatal feline infectious peritonitis (FIP). Independent of virulence variations they are separated into two different types, type I, the original FCoV, and type II, which is closely related to canine coronavirus (CCV). The prevalence of FCoV types in Austrian cat populations without FIP has been surveyed recently indicating that type I infections predominate. The distribution of FCoV types in cats, which had succumbed to FIP, however, was fairly unknown. PCR assays have been developed amplifying parts of the spike protein gene. Type-specific primer pairs were designed, generating PCR products of different sizes. A total of 94 organ pools of cats with histopathologically verified FIP was tested. A clear differentiation was achieved in 74 cats, 86% of them were type I positive, 7% type II positive, and 7% were positive for both types. These findings demonstrate that in FIP cases FCoV type I predominates, too, nonetheless, in 14% of the cases FCoV type II was detected, suggesting its causative involvement in cases of FIP.

Fig. 1

Multiple alignment of partial nucleotide sequences (108 bp) of the S-protein gene region of Austrian FCoV type I (FCoV-1 Au 1–11, GenBank accession no. AF533338-AF533348) and type II (FCoV-2 Au 1–2, GenBank accession no. AY156723-AY156724) positive samples and of one sample with a double infection (FCoV-1 DI and FCoV-2 DI). Reference sequence: FCoV-1 strain KU2 (GenBank accession no. D32044; nt. pos. 4373–4480); also included in the alignment: a reference strain for FCoV-2 (79-1146; GenBank accession no. X06170; nt. pos. 4337–4444) and for canine coronavirus (INSAVC-1; GenBank accession no. D13096; nt. pos. 4770–4877). Light grey-underlay: FCoV type I strains; white: FCoV type II strains; dark-grey underlay: canine coronavirus.

Fig. 2

RT-PCR amplification of cell culture supernatants of five different FCoV strains with the primers fecv1b. Only FCoV type I strains were amplified. M: 100 bp ladder (Amersham Pharmacia), lane 1: strain KU-2, lane 2: negative control, lane 3: strain NW1, lane 4: strain 79-1146, lane 5: strain 79-1683, lane 6: strain DF2.

Fig. 3

RT-PCR amplification of cell culture supernatants of five different FCoV strains employing the primers fecv2b. Only FCoV type II strains were amplified. M: 100 bp ladder (Amersham Pharmacia), lane 1: strain KU-2, lane 2: strain NW1, lane 3: strain 79-1146, lane 4: negative control, lane 5: strain 79-1683, lane 6: negative control, lane 7: strain DF2.